water distribution system

1. WATER DISTRIBUTION AND NETWORK
Layout of distribution networks,
methods of water distribution,
storage capacity of ESR, and
underground service reservoir.

2. Introduction…
The purpose of distribution system is to
deliver water to consumer with
appropriate quality, quantity and
pressure.
Distribution system is used to describe
collectively the facilities used to supply
water from its source to the point of
usage.

3. Requirements of Good Distribution
System...
Water quality should not get deteriorated
in the distribution pipes.
It should be capable of supplying water
at all the intended places with sufficient
pressure head.
It should be capable of supplying the
requisite amount of water during fire
fighting.

4. The layout should be such that no
consumer would be without water
supply, during the repair of any section
of the system.
All the distribution pipes should be
preferably laid one metre away or above
the sewer lines.
It should be fairly water-tight as to keep
losses due to leakage to the minimum.

5. Layouts of Distribution Network
The distribution pipes are generally laid
below the road pavements, and as such
their layouts generally follow the layouts
of roads.
There are, in general, four different types
of pipe networks; any one of which either
singly or in combinations, can be used for
a particular place.

6. They are:
Dead End
System
Radial System
Grid Iron
System

7. Dead End System...
It is suitable for old towns and cities
having no definite pattern of roads.

8. Advantages
Relatively cheap.
Determination of discharges and
pressure easier due to less number
of valves.
Disadvantages
Due to many dead ends, stagnation of
water occurs in pipes.

9. Radial System...
The area is divided into different
zones.
The water is pumped into the
distribution reservoir kept in the
middle of each zone.
The supply pipes are laid radially
ending towards the periphery.

10. Advantages:
It gives quick service.
Calculation of pipe sizes is
easy.

11. Grid Iron System...
It is suitable for cities with rectangular
layout, where the water mains and
branches are laid in rectangles.

12. Advantages
Water is kept in good circulation due to
the absence of dead ends.
In the cases of a breakdown in some
section, water is available from some
other direction.
Disadvantages
Exact calculation of sizes of pipes is
not possible due to provision of
valves on all branches.

13. Ring System...
The supply main is laid all along the peripheral
roads and sub mains branch out from the
mains.
 This system also follows the grid iron system
with the flow pattern similar in character to that
of dead end system.
So, determination of the size of pipes is
easy.

14. Advantag
es
Water can be supplied to any point
from at least two directions.

15. Methods of water distribution…
For efficient distribution system adequate
water pressure required at various points.
Depending upon the level of source,
topography of the area and other local
conditions the water may be forced into
distribution system by following ways -

16. 1. Gravity system
2. Pumping system
3. Combined gravity and pumping
system

17. Gravity system…
Suitable when source of supply is at
sufficient height.
Most reliable and economical
distribution system.
The water head available at the consumer
is just minimum required.
The remaining head is consumed
in the frictional and other losses.

19. Pumping system…
Treated water is directly pumped in
to the distribution main with out
storing.
Also called pumping without storage
system.
High lifts pumps are required.
If power supply fails, complete stoppage of
water supply.
This method is not generally used.

21. Combined gravity and pumping system
Most common system.
Treated water is pumped and stored
in an elevated distribution reservoir.
Then supplies to consumer by action of
gravity.
The excess water during low demand
periods get stored in reservoir and get
supplied during high demand period.
Economical, efficient and reliable system.

23. Distribution Reservoirs...
Distribution reservoirs, also called
service reservoirs, are the storage
reservoirs, which store the treated
water for supplying water during
emergencies (such as during fires,
repairs, etc.) and also to help in
absorbing the hourly fluctuations in the
normal water demand.

24. Functions of Distribution Reservoirs
 to absorb the hourly variations in demand.
 to maintain constant pressure in the
distribution mains.
 water stored can be supplied during
emergencies.
Location and Height of Distribution Reservoirs
 should be located as close as possible to the
centre of demand.
 water level in the reservoir must be at a
sufficient elevation to permit gravity flow at
an adequate pressure.

26. Types of Reservoirs...
Depending upon their elevation w.r.t
ground it may be classified into
1. Surface reservoirs
2. Elevated reservoirs

27. Surface reservoirs…
These also called ground reservoir.
Mostly circular or rectangular tank.
Under ground reservoirs are
preferred especially when the
size is large.
These reservoirs are constructed on
high natural grounds and are
usually made of stones, bricks, plain
or reinforced cement concrete.

28. The side walls are designed to take up
the pressure of the water, when the
reservoir is full and the earth pressure
when it is empty.
The position of ground water table is
also considered while designing these
reservoirs.
The floors of these reservoirs may
constructed with R.C.C slab or square
stone blocks resting on columns.

29. To obtain water tightness bitumen
compounds are used at all construction
joints.
At the top of roof about 60cm thick earth
layer is deposited and maintained green
lawns to protect the reservoir from cold
and heat.
For aeration of water and inspection,

30. Under Ground Reservoir

31. TYPES OF
TANKS
C.TANKS: R.C.C tanks are very popular
because
1)They have long life
2)Very little maintenance
3)decent appearance

32. G.I. TANKS: G.I. tanks are generally in
rectangular or square in shape. Now a
days G.I. tanks are not preferring
because
1)Life of the tank is short
2)Corrosion of metal
3)maintenance cost may be
more

33. HDPE TANKS: Now a days HDPE tanks
are very popular for storing less quantity
of water and hence useful for residential
purpose. The following are the
advantages of HDPE tanks
1)Handling is easy because of light
weight
2)Cheap in cost
3)Maintenance cost is low
4)Cleaning of tanks are easy

34. ESR...
Elevated Storage Reservoirs (ESRs) also
referred to as Overhead Tanks are
required at distribution areas which are
not governed and controlled by the
gravity system of distribution.
These are rectangular, circular or
elliptical in shape.
If the topography of the town not suitable
for under gravity, the elevated tank or
reservoir are used.

35. They are constructed where combine
gravity and pumping system of water
distribution is adopted.
These tanks may be steel or RCC.
Now RCC is commonly preferred.

36. The accessories of ESR are-
Inlet and outlet pipe, overflow pipe
discharging into a drain
Float gauge, indicating depth of water.
Automatic device to stop pumping
when the tank is full.
A manhole and ladder.
Ventilator for circulation of fresh air.

38. Storage Capacity of Distribution
Reservoirs...
The total storage capacity of a
distribution reservoir is the
summation of:
Balancing Storage: The quantity of
water required to be stored in the
reservoir for equalising or balancing
fluctuating demand against constant
supply is known as the balancing
storage (or equalising or operating
storage).

39. Breakdown Storage: The breakdown
storage or often called emergency
storage is the storage preserved in order
to tide over the emergencies posed by
the failure of pumps, electricity, or any
other mechanism driving the pumps.
A value of about 25% of the total
storage capacity of reservoirs, or 1.5 to
2 times of the average hourly supply,
may be considered as enough
provision for accounting this storage.

40. Fire Storage: The third component of
the total reservoir storage is the fire
storage.
This provision takes care of the
requirements of water for extinguishing
fires.
A provision of 1 to 4 per person per
day is sufficient to meet the
requirement.

41. When reserve storage is elevated,
amount of fire reserve may be
determined by
R= (F-P) T
R= Reserve storage (liters)
F= Fire demand, liters/min
P= Reserve fire pumping capacity,
liters/min
T= Duration of the fire in min
The total reservoir storage can finally